Influence Of Acid Treatment Research Articles

The influence of acid treatment on the adsorption‑structural characteristics of filtering materials created based on steelmaking slag

Many industrial enterprises use electroplating processes that lead to the formation of water containing heavy metal ions such as chromium, copper, zinc, nickel, and others. Such water is a dangerous source of environmental pollution. Most heavy metal ions belong to hazard classes I–II, they have carcinogenic and mutagenic properties, and have a cumulative effect.The literature analysis showed that there is positive experience in the use of steelmaking slags in the processes of cleaning contaminated water of various origins from heavy metals.The study examines the effect of acid activation on the adsorption‑structural characteristics of filtering materials created based on steelmaking slag. It is shown that during the interaction of some acids with slag, new crystallographic phases are formedon its surface, and contact with other acids leads to the leaching of ions and their transition to the aqueous phase. It has been established that during acid activation, the specific surface area increases by 57–132 times compared to the original material.

Synthesis of mesoporous carbon particles with different pore sizes by soft template method

The Stöber method provides a facile procedure for making carbon spheres with controlled particle sizes and is considered to be low-cost. In this study, a facile method has been established for synthesizing porous carbon spheres with variable pore sizes using a modified Stöber process. The influence of acid treatment and manipulating the carbonization process heating rate on the pore size and morphology of the particles was investigated by nitrogen adsorption, Scanning Electron Microscopy (SEM), Powder X-ray diffraction (XRD), Raman and Fourier Transform Infrared Spectroscopy (FTIR). According to the results, carbon spheres were in the size range between 1 and 7 microns. Pore size characterization shows that the pore diameter has increased by increasing the heating rate as well as by performing acid treatment. Tunable pore sizes from 2.25 to 8 nm have been evidenced by the experiments. These synthesized mesoporous carbons with different pore sizes which facilitate penetration of molecules and ions are promising as effective materials for adsorption, encapsulation and material delivery applications.

Influence of functional carbon nanotube and multi‐cyclic shape memory performance on thermally triggered polyurethane nanocomposites

AbstractIn this study, thermally triggered shape memory thermoplastic polyurethane‐multiwall carbon nanotube (TPU/MWCNTs) nanocomposites with varying nanofiller content (0–5 wt%) were prepared. Melt flow, morphology, and shape memory properties of TPU/MWCNTs nanocomposites were investigated. We attempt to clarify the reinforcement effect of CNTs on the shape memory behavior of TPU/MWCNTs nanocomposites. Moreover, the influence of acid treatment on surface morphology, thermal stability, and dispersion state of MWCNTs has been evaluated. Pristine MWCNTs were treated with highly concentrated nitric acid (68%) and introduced by solution mixing to TPU as an efficient reinforcement phase. The thermogravimetric analysis revealed thermal stability improvement of acid treatment MWCNTs. Field emission‐scanning electron microscopy images confirmed the homogenous distribution of oxidized MWCNTs in the matrix and some aggregated structures at 5 wt% nanofiller. Higher melt flow rate values were observed for composites loaded with 0.5–1 wt% ox‐MWCNTs compared with 2–5 wt% because of their better dispersion in TPU. The experimental results show a higher shape recovery ratio of TPU/ox‐MWCNTs nanocomposites than pure polyurethane (over 20%). A good shape recovery in the 90%–100% range could be obtained during a shape recovery test when ox‐MWCNTs content of 0.5–2 wt% is proposed to synthesize TPU/ox‐MWCNTs nanocomposites.

Influence of acid treatment on flavonoid content and biological activity in tartary buckwheat grains and its application for noodles

Acid treatment is one of the most effective methods to convert flavonoid glycosides into their aglycones. In this study, the impacts of acid treatment of tartary buckwheat grains on the flavonoid composition and biological activities of tartary were investigated. The results indicated that acid treatment allowed the deglycosylation of rutin to quercetin in buckwheat grains, contributing to the enhancement of their antioxidant activity. Furthermore, as compared to the non-treated sample, acid-treated buckwheat grain samples showed stronger inhibition on tert-butyl hydroperoxide mediated the formation of intracellular reactive oxygen species in HepG2 cells, reduction in lipid accumulation and the related adipogenic transcription factors in 3T3-L1 cells, and reduction in inflammatory mediators in RAW 264.7 cells. Upon application to noodles making, noodles supplemented with acid-treated tartary buckwheat flours, which had weakened gluten strength and a low degree of gelatinization, displayed significantly improved antioxidant activity. These findings suggest that acid-treated buckwheat flours can be used to improve the health benefits of buckwheat products.

Influence of Acid Treatment on the Loading and Release Behavior of Halloysite with 2-Mercaptobenzothiazole

Halloysite nanotubes (HNTs) are natural clay minerals with a tubular structure. They have attracted considerable attention as a potential nanocontainer due to their abundance, biocompatibility and nontoxicity. In this study, HNTs were handled with H₂SO₄ at 70 °C. The morphology and structure of these acid-treated and original HNTs were investigated by scanning electron microscopy (SEM), energy dispersion spectrum (EDS), transmission electron microscope (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR), and their specific surface area was determined by automatic gas adsorption analyzer. The loading efficiency and release behavior of acid-treated HNTs for 2-Mercaptobenzothiazole (MBT) were investigated by UV-vis spectrophotometer. Results show that acid-treated HNTs retained their tubular structure, but their internal diameter expanded by 35-37 nm after 32 h of acid treatment. After 72 h of acid treatment, HNTs can be transferred into amorphous silica nanotubes. Moreover, the specific surface area of these HNTs samples initially increased with the increase in acid treatment time but then started to decrease after 32 h. The specific surface area of acid-treated HNTs at 32 h can reach 251.6 m₂/g, which was much higher than that for untreated HNTs (55.3 m₂/g). In addition, the loading capacity of acid-treated HNTs can reach 32.1% for HNTs-32, which is about three times higher than that of original HNTs. The acid treatment has slight effect on the release behavior.

Influence of acid treatment and carbonation on the properties of recycled concrete aggregate

Recycled concrete aggregate (RCA), obtained by crushing of original (old) concrete, consists of natural aggregate grains and a cement mortar matrix. The presence of old adhered cement mortar, which has higher porosity than natural aggregate, causes unfavourable properties of RCA. The research conducted in order to improve the quality of RCA and to enable its greater application in the construction industry is presented in this paper. Therefore, RCA was subjected to quality improvement treatments with hydrochloric acid and carbon dioxide (accelerated carbonation). The first procedure was aimed at partially removing the adhered cement mortar and the second at reinforcing the cement matrix. The physical, mechanical and chemical properties of all three types of RCA were tested. After the pre-soaking acid treatment (0.1 mol/dm3 HCl), RCA showed reduced water absorption (up to 3%); the process of accelerated carbonation also led to reduced water absorption (13?20%) as well as to improved mechanical properties (?10%). A scanning electron microscopy investigation revealed that the carbonation process, as expected, significantly reduces porosity of RCA. The overall results show that if RCA is obtained by crushing of compact, high- -quality concrete, the procedures of aggregate quality improvement are not necessary.

Electrochemical corrosion behavior of acid treated strip cast AM50 and AZX310 magnesium alloys in 3.5 wt.% NaCl solution

Abstract The influence of acid treatments on the surface morphology and electrochemical corrosion behavior of strip-cast AM50 and AZX310 alloys have been studied in the present investigation. The alloys were acid treated using H 3 PO 4 (AT-1) , HF (AT-2) and HNO 3 (AT-3) for different treatment durations viz., 60, 300 and 600 s. The acid treatments produced a surface layer consisting of corresponding magnesium salts of the acids and were confirmed from the X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX). AT-1 treatment produced cracked and network porous morphology for AM50 and AZX310 alloys respectively and AT-3 treatment exhibited dense creaked surface layer formation while AT-2 does not produce any significant change in the morphology. Polarization studies revealed that, the acid treatment significantly altered the corrosion process by altering anodic and cathodic reaction rates of AM50 and AZX310 alloys. The HNO 3 (AT-3) treatment was effective compared to other treatments to control the corrosion rate in the studied treatment conditions. The surface morphology and chemical composition of surface layer produced during the treatment was correlated to explain the corrosion results.

Fischer–Tropsch Synthesis: Influence of Acid Treatment and Preparation Method on Carbon Nanotube Supported Ruthenium Catalysts

The influences of nitric acid treatment on a carbon nanotube (CNT) support and the preparation method, incipient wetness impregnation (IWI) versus chemical vapor deposition (CVD), on catalytic performance during Fischer–Tropsch (FT) synthesis were examined using a slurry phase reactor. Acid treated CNT (ACNT) supported Ru catalysts exhibited higher activities compared to Ru supported on untreated CNTs (UCNTs). The acid-treated CVD catalyst had higher initial CO conversion (smaller average Ru particle size) but sintered more due to a greater tendency for Ru to be deposited exterior to CNT channels relative to IWI. After the initial decline and leveling off period, the ACNT IWI catalyst had the highest steady activity among the catalysts tested. The ACNT IWI catalyst also displayed greater oxygenate selectivity (∼17%) compared to ACNT CVD (∼12%) and UCNT IWI (∼10%) catalysts at similar conversions. Acid treatment created adsorption sites on the CNT surface that anchor Ru precursors and promote CO insertion ...

Influence of Acid Treatment on Properties of Dry-spinning Jialun Polyimide Fibers Reinforcement

Influence of Acid Treatment on Properties of Dry-spinning Jialun Polyimide Fibers Reinforcement

Thermal stability of tetrabutyl-phosphonium and -ammonium exchanged montmorillonite: Influence of acid treatment

Thermal stability of acid-treated organo-montmorillonites was investigated by thermogravimetric analysis (TA) coupled with infrared (IR) spectroscopic analysis of evolved gasses, and by in-situ measurement of near-IR (NIR) spectra of solid samples. The organoclays prepared from Na-form of SAz-1 montmorillonite (Na-S) and tetrabutylphosphonium (Bu4P+) and tetrabutylammonium (Bu4N+) salts were treated with 6M HCl at 80°C for 2–12h. Elemental analysis revealed higher resistance of Bu4P-S and Bu4N-S to decomposition compared to Na-S, leaving 44 and 52% of the octahedral Mg and/or Al in the solid reaction products after 12h treatment. Bu4N-S decomposed in slightly lower extent than Bu4P-S, pointing thus to the influence of the type of cation headgroup on its stability in HCl. The TG/DTG profiles of both samples showed pronounced mass loss due to decomposition of organic cations within temperature 200–800°C. While Bu4N-S showed onset temperature of near 200°C, significantly higher temperatures, above 300°C, was found for Bu4P-S. The intensities of the absorption bands related to CH vibrations of aliphatic hydrocarbons in the IR spectra reached maxima at 277°C and 446°C for Bu4N-S and Bu4P-S, respectively. The mass loss attributed to the organic cation decomposition for acid-treated samples dropped down below 50% of its initial value due to the leaching of organic phase. Moreover, the onset temperature of organic phase release was shifted to higher temperature indicating that only more strongly held cations remained in the samples. NIR spectra showed that the intensity decrease of the first 2νCH overtones band due to organic cation release began at lower temperature for Bu4N-S (above 380°C) than for Bu4P-S (above 500°C).

Influence of Acid Treatment on Physicochemical Properties of Aged Rice Flour

This study investigated the influence of citric acid and ascorbic acid solutions (0.0–0.9% w/w) on the physicochemical properties of 12 month aged rice flour (aged) using 0.7 month rice flour (fresh) as the reference. The results showed that rice storage did not affect the chemical composition. However, 12 month aged rice flour showed an increase in formation of disulfide bonds and amylose-lipid complexes which could restrict starch granules from swelling during gelatinization. Moreover, 12 month aged rice flour showed an increase in gelatinization temperature and enthalpy. Acid treatment did not break the formed disulfide bond but reduced the protein content in the acid-treated 12 month aged rice flour producing a significant increase in granular swelling and thus increased peak viscosity (p ≤ 0.05) but caused a reduction in retrogradation. The excess concentration (0.9% w/w acid solution) induced granule rupture. Aging of rice also affected the textural properties of freeze-thaw gels, increasing the hardness value but this was reduced by the addition of acids.

The influence of acid treatments over vermiculite based material as adsorbent for cationic textile dyestuffs

The influence of different acid treatments over vermiculite was evaluated. Equilibrium, kinetic and column studies have been conducted. The results showed that vermiculite first treated with nitric acid and then with citric acid has higher adsorption capacity, presenting maximum adsorption capacities in column experiments: for Astrazon Red (AR), 100.8 ± 0.8 mg g−1 and 54 ± 1 mg g−1 for modified and raw material, respectively; for Methylene Blue (MB) 150 ± 4 mg g−1 and 55 ± 2 mg g−1 for modified and raw material, respectively. Materials characterization by X-ray diffraction, UV–vis-diffuse reflectance spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, X-ray fluorescence, N2 adsorption and CEC determination, has been performed. The results suggest the existence of exchange of interlayer cations, leaching of metals from vermiculite's sheets and formation of an amorphous phase in the material. Adsorption follows pseudo 2nd order model kinetics for both dyestuffs and equilibrium occurs accordingly to Langmuir's model for AR and Freundlich's model for MB. In column systems Yan's model is the best fit. The enhanced properties of acid treated vermiculite offer new perspectives for the use of this adsorbent in wastewater treatment.

Influence of acid treatment on structure of clinoptilolite tuff and its adsorption of methane

This study presents the results of the methane adsorption properties of clinoptilolite tuff from Bigadic, Turkey and that of acid treated forms at 273 and 293 K up to 100 kPa using volumetric apparatus. In order to assess changes in structural and gas adsorption properties of clinoptilolite, zeolite sample was treated with acid solutions of varying concentrations (0.1, 0.5, 1.0 and 2.0 M) at 70 °C during 3 h. Structural and thermal characterization of natural and acid treated clinoptilolite samples were carried out using a combination of techniques such as X-ray diffraction, X-ray fluorescence, thermogravimetric, differential thermal analysis and nitrogen adsorption methods. At both temperatures, uptake of methane (CH4) increased in the following order: CLN < CLN-H2 < CLN-H1 < CLN-H05 < CLN-H01. CH4 adsorption capacities of the original and acid treated clinoptilolites were found in the range of 0.476–0.910 mmol/g and 0.398–0.691 mmol/g at 273 and 293 K, respectively.

Influence of acid treatment on N-doped multi-walled carbon nanotube supports for Fischer–Tropsch performance on cobalt catalyst

Nitrogen-doped carbon nanotubes (NCNTs) were acid treated and used as a support for Co catalysts. The effect of acid treatment time on the carbon structure, surface properties and the microstructure of Co catalysts was extensively characterized by BET, XRD, TPR, XPS, TEM and Raman spectroscopy. It was found that acid treatment affected the support structure, the Co reducibility, the Co dispersion and the Fischer–Tropsch (FT) synthesis performance significantly. The graphitization degree, cobalt particle size, cobalt particle location and the number of active sites determined the FT synthesis performance of the Co catalysts.

Effect of acid treatment and dipping time on the performance of CdS quantum dot solar cells

Semiconductor quantum-dot-sensitized TiO 2 thin-film solar cells have been assembled by incorporating CdS quantum dots into the TiO 2 porous film. The influence of acid treatment on TiO 2 electrode, dipping time, and the effect of electrolytes on the performance of solar cells have been investigated. Two types of solar cells have been fabricated, one using a liquid electrolyte and the other one using a quasi-solid-state polymer electrolyte. It has been found that quantum-dot-sensitized solar cells exhibits better photovoltaic performance when the TiO 2 electrode was acid-treated. When the TiO 2 electrode was acid-treated, the short-circuit current, open-circuit voltage, fill factor, efficiency, and even the amount of quantum dots absorbed by the TiO 2 film was found to increase appreciably. The quantum dot solar cells fabricated using liquid electrolyte were observed to exhibit better efficiency than the quasi-solid-state polymer-electrolyte-based solar cells.

The influence of acid treatment on multi‐walled carbon nanotubes

PurposeThe purpose of this paper is to investigate in detail the effects of acid treatment on multi‐walled carbon nanotubes (MWNTs), which could find a variety of applications in coatings and composites.Design/methodology/approachA number of analytical techniques, including Fourier transform infrared spectroscopy (FT‐IR), X‐ray photoelectron spectroscopy (XPS), Raman spectroscopy (Raman), and scanning electron microscopy (SEM), were employed to assess the effects of acid treatment on MWNTs.FindingsIt was found that desirable modifications to MWNTs occurred after acid treatment. Thus, carboxylic acid groups were introducing on to the surface of MWNTs. It was also found that both chemical and physical properties of MWNTs could be modified/altered.Practical implicationsThe investigation established a method to modify MWNTs via acid treatment and the effects of such a treatment on MWNTs in detail. The modified MWNTs can be used for various applications and further modifications. The acid treated and the further modified MWNTs can be dispersed into polymers to prepare polymer/MWNTs composite materials and composite surface coatings. Some properties of the resulting composites were improved by the dispersed MWNTs, giving excellent mechanical, electrical, thermal and magnetic properties.Originality/valueThe finding on the effects of acid treatment on MWNTs, supported by detailed FT‐IR, XPS, Raman and SEM data, would be of interest to the field. The modification technique provided a route to further modification of carbon nanotubes. The acid treated and the further modified MWNTs are useful for preparation of polymer/MWNTs composite materials and composites surface coatings with improved mechanical, electrical, thermal and magnetic properties.

Fischer–Tropsch synthesis over carbon nanotubes supported cobalt catalysts in a fixed bed reactor: Influence of acid treatment

The influence of acid treatment on carbon nanotubes (CNT) supported cobalt catalysts for Fischer–Tropsch synthesis (FTS) is discussed in this paper. CNTs were first treated with 30 wt.% HNO 3 at 25 and 100 °C for 14 h. Cobalt catalysts supported on fresh and acid treated carbon nanotubes were prepared using the incipient wetness impregnation method with a cobalt loading of 10 wt.%. The catalysts were extensively characterized by BET, XRD, TPR and TEM, and Raman spectroscopy. The TEM analyses of the acid treated support catalysts showed that the major parts of the cobalt particles were homogenously distributed inside the nanotubes. Raman I D/I G band intensity ratios as an indication of the quality of carbon nanotubes for catalyst supports, increased with acid treatment. The FTS activity (g HC produced/g cat./h) and selectivity (the percentage of the converted CO that appears as a hydrocarbon product) of the catalysts were assessed and compared with the as-prepared CNT supported 10 wt.% cobalt catalyst using a fixed bed micro-reactor. The acid treatments at 25 and 100 °C respectively, (a) increased the BET surface area by 18% and 25%; (b) decreased the cobalt particle size and increased the cobalt dispersion; (c) increased by 10 and 50% the reducibility of the catalysts and (d) increased the FTS activity and %CO conversion by 36 and 114%. Finally, the product selectivity showed a distinct shift to lower molecular weigh hydrocarbons.

Effect of surface shallow traps on flashover characteristics across machinable ceramic in vacuum

The electrical strength of the surface of low-temperature melting machinable glass ceramic, prepared by using several different methods, is investigated before and after treatment with diluted hydrofluoric acid (HF). Using the surface potential decay method, the surface trap density and the energy of each sample are measured. The influence of acid treatment on the trap distribution is analyzed. Concurrent optical and electrical measurements allow surface flashover phenomena in vacuum under impulse voltage to be investigated, along with the influence of surface trapping parameters on flashover performance. It is shown that the glass phase on the surface of machinable ceramic greatly influences the shallow traps, which in turn degrade the flashover characteristics. Removing the glass phase with HF treatment reduces the concentration of shallow traps and stabilizes the flashover voltage.

Erratum to: The influence of acid treatment on the composition of bentonite

In the paper ‘The influence of acid treatment on the composition of bentonite’ from Clays and Clay Minerals, vol. 54 (2006), 699–704, by A. Vulkovic et al., in the list of authors, please replace Aleksandra Milutinovic with Aleksandra Milutinovic-Nikolic.

Filling of carbon nanotubes for bio‐applications

AbstractCarbon nanotubes (CNT) provide a smart carrier system on the nanometer scale. The system can be used as a template for ferromagnetic fillers. Such a molecular hybrid is a promising potential candidate for the controlled heating of tumour tissue at the cellular level. This is a key reason why it is important to optimize the synthesis route of metal filled carbon nanotubes with regards bulk scale synthesis and purity. In the current study we present multiwalled carbon nanotubes filled with α‐iron phase (Fe‐MWCNT). The influence of acid treatment on the stability of the filling and the sample purity is also presented. High resolution transmission microscopy, its Energy dispersive X‐Ray spectroscopy (EDX) and electron energy‐loss spectroscopy (EELS) modes have been applied for the analysis of the morphology and chemical composition of the samples. The phase of iron nanowires encapsulated into the carbon nanotubes was determined with selected area electron diffraction (SAED) on a local scale. (© 2007 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)